The state-of-the-art automatic CVT used in vehicles (like scooters, cars etc) comprises a pair of pulleys, each pulley made up of two, conical, sliding halves with a fixed length V-belt running between them. The engine drives the one pulley; the other pulley drives the wheel(s). When the one pulley closes up, the belt has to force the other pulley apart. When the one pulley's halves are forced completely together, the halves of the other pulley are forced completely apart.
As the pulleys move apart and close together, the gearing varies continuously.
In some CVT's of the state-of-the-art the gear ratio shifts automatically by the variator. The variator is a disc-shaped assembly fitted to the same shaft as the first pulley. It has a sloped section and carries a number of weights in a cage around the disc. As the variator assembly spins, the weights react to the centrifugal force and try to move outwards. As they do so, the weights climb the ramp and force the first pulley to close, which in turn forces the second pulley to open and this raises the gearing. When the throttle closes, the centrifugal force is reduced and the weights drop back, allowing the first pulley to open slightly, which allows the belt to ride lower within the two halves of the first pulley, which in turn allows the second pulley to close up and so the gear ratio lowers.
The driver (or the user in general) has not the option to select the transmission ratio of his desire. The tuning of the CVT in the factory (geometry of the pulleys/belt/variator, mass of the weights, springs used etc) is a compromise for:
relatively acceptable fuel efficiency (mileage),
relatively acceptable acceleration,
relatively acceptable final speed,
relatively acceptable reliability,
relatively acceptable climbing ability,
relatively acceptable operation etc.
However the user of the CVT may have different priorities, or priorities that vary depending on the instant conditions (traffic, gradient of the road, opposite wind, need for quiet operation, need for top acceleration etc).
This explains the demand for aftermarket variators. With a different, or a modified, variator the CVT operates/behaves differently. By putting heavier weights in the same variator, the revs of engagement drop, the vehicle runs quieter at lower revs, the mileage increases, the CVT is more reliable; however the acceleration drops, an opposite wind or a steep uphill may become significant problems, etc. By putting lighter weights in the same variator, the revs of engagement increase, the vehicle accelerates faster, the climbing on a steep uphill is easy, the strong opposite wind is not a problem; on the other hand the noise increases, the mileage drops, the time between overhauls drops.
The problem comes from the fact that today the rider/driver/user of the typical “automatic” CVT has not the option to substantially vary the operational characteristics of the CVT “on-the-fly”. The low cost automatic CVT's of the art are of the type: “take it, or leave it”; the user/rider has to adapt himself to the characteristics of the CVT, not the opposite.
It is an object of the present invention to address the above disadvantages. Accordingly, there is provided a simple, reliable and efficient mechanism for the control of the V-belt CVT's as defined in the appended claims.